Hardware supplied by Hewlett Packard Enterprise has malfunctioned, causing a major IT outage at the Australian Taxation Office, with staff unable to use systems on Monday and Tuesday.
A Fairfax Media report said that the ATO was trying to recover about one petabyte of unspecified data.
It said the ATO's woes were caused by hardware that was supplied just 13 months ago by HPE, one of the firms that was listed by the ATO recently as having paid no tax in 2014-15.
The ATO's online systems for the public still appear to be offline at the time of writing (0800 AEDT on Wednesday).
{loadposition sam08}Many employees were sitting idly by on Tuesday afternoon, unable to use their computers for a second day running.
Fairfax said ATO staff were insistent that no taxpayer information had been lost due to the hardware problems.
The systems first crashed on Sunday night or Monday morning.
Contacted for comment, the ATO pointed iTWIre to a media release issued at 1838 AEDT on Tuesday. It read: "Our website is now back online at ato.gov.au for you to access tax and super information. Thank you for your patience.
"You may find you’re unable to access certain tools, calculators and our online services (such as the portals) while we continue working to restore all of our services.
"If you’re still seeing a website maintenance page when you visit the site, we recommend clearing your browser cookies and cache."